Dry ice storage



w. T. BIRDsALL DRY ICE STORAGE Filed Nov. 4, 1957" Jan. 6, 1942.

Patented Jan. A 6? '194% UNITED STATE S PLA'I'ENT- OFFICE DRY' ICE STORAGE wilma vr. mrasau, deceased, ma of N. .1., by Alvin o. Boussu, ummm ington, D. C., assignor to Montclair, tonw Mergcnthaler Linotype Company, Brooklyn, N. Yea corporation of New York Y, Application November 4, 1937,

serial No. 112,717

'(01. sas-91.5)

The storage-of dry ice ona large scale or for long periods of time has heretofore been economically impractical due primarily to the very low temperature of the material and the -diftlculty in maintaining the requisite temperature difference between the stored material and the external atmosphere. The most effective devices now known to the industry for protecting dryice from external heat serve only to reduce the loss by evaporation to from 5 to 10 per cent of the stored material per day. Such losses are obviously so great that storage for periods of weeks or months is impossible. Furthermore dry ice is usually manufactured and sold in the form of blocks of standard size and shape, which on standing lose their regular shape so that when cut up into smaller pieces much of the block is wasted as scrap. y

-The means most commonly employed. at the;` present time for protecting dry ice during ship-"- ping and storing are balsa-wood boxes of varying thickness. It has also been proposed to util-ize the gas produced by evaporation of dry ice for cooling a refrigerated space but the problem in such cases has` been to use only a small quantity of dry ice while maintaining the temperature of the space sumciently low to prevent destruction or decay of fruit, fish, ice cream or the like.

In accordance with the present invention, it is possible to reduce the loss of stored dryice to such an extent that it may be stored for long periods of tlmeby establishing a heat absorbing zone which takes up and removes substantially all heat that-penetrates the insulation about the zone. Then by insulating the storage chamber from the zone so produced it is possible to subproduced and circulated about storage space may have a temperature even beblocks are greatly reduced.

large surface and therefore evaporates much more rapidly than the stored ma erial' the gas e insulated low that of the stored material. By this rmeans it has been found possible to reduce the loss of the stored material to a small fraction of one per cent per day without substantially increasing the size or cost of the storage apparatus. The blocks retain their regularity of shape and rm structure so that losses occurring on cutting the One of the objects of the present invention is to providel new and improved means for preservving dry ice.

Another object of the invention is to preserve blocks of dry ice for long periods of timewith substantially the form and structure that they possess when ilrst produced.

A :lurtherl object of the invention is to utilize brokenor scrap dry ice in the preservation of blocks of d'ry ice being stored.

These and other objects and features of the invention will appear from the following descriptionin which reference is made to the. accom- Danying figures of the drawing which illustrate a typical form of mechanism -adapted for use `in the practice of applicants invention.

In the drawing:

Figure 1 is avertical sectional view of a repre- Y ,A

sentative form of apparatus for use in the storage of dry ice in accordance ywith applicants invention. I l. lf

vFigure 2 is a horizontal s ional view taken on the line 2 -2 of rFigure l, and f Figure 3 is a horizontalsectional view taken onthelinel-fiofllgurel y In that form ofthe invention chosen for pur --poses of illustration in the figures of thedrawing,

a storage receptacle designed to receive a small number of blocks of dry ice is shown, but it f should be understood that the invention is equally applicable to the storage of large quantities of the material. The storage chamber shown comprises an outer 'casing 2 suitably insulated with balsa-wood, cork, or other insulating material and provided with a cavity 4 which may be lined with metal 6 if desired toprovide a surface of substantially uniform temperature throughout. Within the cavity I is located a sleeve l which preferably is formed of insulating'y material and is supported in spaced relation to the bottom of the cavity by supports Il so as to provide a channel Il extending about the bottom and sides of the inner wall of the sleeve through which gas descending inthe channel 20 may pass to the opening I6 and thence to the channel I2 about' the exterior of the sleeve.

A heat insulating storage chamber 24 for receiving the blocks of dryl ice to be stored is located within the sleeve 8 and is' provided with channels 26 in itsouter surface which are separated from the channels 2n by the separator I8.

-The channels 26 and 20 join at the bottom of the receptacle so that gas from both channels passes beneath the storagechamber to the opening I6. Blocks of dry ice 28 being storedv are placed within the storage chamber and preferably' are 1 enclosed within'permeable insulating covers 30 in the forml of felt-lined jackets tting closely about the blocks of dry ice. Such covers or jackets are described more fully in applicants copending application, Serial No. 172,714, nled Nov. 4, 1937, wherein applicant has pointed out the function thereof in reducing or retarding diiusion of gasfrom the solid. Any number of blocks may be -positioned within the storage chamber and they may be arranged as desired in order to store as much material as possible in a small space and avoid creating convection currents about the stored. material. As shown the inner walls of the storage chamber are formed with channels 84 shown in Figure 3, to provide passages for the flow of gas from the stored material into the channel 26 about the exterior of the reeepticle. The upper edge of the chamber .ceptacle into the channels 20 flowing downward- 1y within the sleeve 8 about the separator I8 and beneath the storage chamber 24 to the opening' I6 in the support I4 for the sleeve. Thence the gas ows outwardly to the channels I2 and `upwardly again to the space 46 completing the circuit.

As shown in Figures 2 and 3 the downwardly extending channels 28 and the upwardly extending channels I2 may be arranged in staggered relation to provide the maximum cooling and absorptlony of heat from the sleeve 8. In this way transfer of heat by conduction through the insulating sleeve 8'from channels I2 tothe channels 28is reduced to a minimum and the inner` surface of the sleeve is maintained at a temperature approaching that of the cold gas circulating downwardly over the same.- Transfer of heat 'from the sleeve to the downwardly iiowing gas is thus negligible and the heat absorbing zone produced is itself at a temperature substantially as low or even lower than that of the stored material.

As shown in the drawing the sleeve 8 is of greater thickness adjacent the top thereof than near the bottom whereas the storage chamber 24 is thicker adjacent the bottom than at the top. This construction is desirable in many instances,

due to the fact that the evaporating broken dry is formed with openings 36 to provide communication between the passages 34 and the channels 26.

In orderto preserve the stored dry ice by localizing the absorption of heat from externalv sources and by providing a low temperature heat absorbing zone, the device is provided with a receptacle -88 positioned above the storage chamber 24 and formed to close the upper end thereof, leaving only the openings 36 for the escape of what little gas may evaporate from the stored material. The receptacle 88 is charged with broken or scrap dry ice or withother suitable low temperature material and is formed with openings 40 in the lower portion thereof communicating with the channels 28 which extend downwardly about the exterior of the separator I8. A cover 42 is provided for-the receptacleand is formed with an opening 44 in the center thereof communicating with the space 46 between the cover 42 for the receptacle and the cover 48 for the casing 2. wardly about the sides of the sleeve 8 communi- 'I'he channels` I2 which extend up@ ice cools the adjacent blocks of'stored material \to a greater extent than the circulating gas passingdownwardlyI through the channels 28 and 26. Thelower portion of the chamber 24 is'thus provided with the maximum heat insulation through .that portion thereof subjected to the highest external temperature. The receptacle 38 within which the broken dry ice is maintained 'is also provided with additional insulation about the top thereof by thickening the top of sleeve 8 to compensate for the absence of downwardly circulating cold gas about the same.

In using the construction described, the blocks of dry ice to be stored are placed in the pervious cate with the space 46 through openings .5U--

4about the upper edge of the sleeve 8 so that gas Vflowing upwardly through the channels I2 passes into the space 46 and through the central opening 44 in the cover 42 into contact with the broken dry ice 52 within the receptacle. The gas is thus cooled by evaporation of the broken dry ice and flows downward through an'd over. the same giving up all heat penetrating the insulating casing 2 to the dry ice in the receptacle. The cold heavy gas then passes outwardly through the openings 4lin the loweriportion of the re- Jackets 38 and introduced into the storage chamber 24 to substantially ll the same, the blocks being arranged in any desired manner to facilitate their removal and to avoid the creation of convection currents within the. eceptacle itself. The receptacle 38 is then place above the storage chamber 24 to substantially close the same and is charged with broken dry ice or any other suitable refrigerant. 'I'he cover 42V of the receptacle 38 is located in place andthe cover 48 for the casing 2 is applied. Ordinarily a pervious insulating packing 54' is located between the cover and the casing to permit the escape of carbon dioxide gas produced while preventing transfer of heat or the ,admission of air to the material through the space thus created. The cover 48 may be removed from time to time as necessary to renew the charge of broken dry ice within the receptacle 38.

The creation of the currents-of gas through the chasm-els 20 and I2 takes place automatically and varies with the rate of circulation and evaporavtion of broken dry ice. This variation occurs in response to the rate of heat transfer through the walls of the casing 2. Therefore a heat absorbing zone is established about the storage chamber which is continuously and automatically maintained at or below the temperature of the stored material itself.v 'I'he supply of cold gas is continuously renewed and that portion thereof passing over the surface of the storage chamber within which the material is locatedisat the lowest temperature produced in the ap paratus. Furthermore the low temperature zone itself is. insulated from external dheat bythe upwardly flowing current of gas in the channels I2 and by theinsulating sleeve 8. All heat absorbed by the gas during its circulation is extracted therefrom by its passage through the r`e\.

ceptacle 38 from the central opening M to the outlets 40 whereby it gives up its heat to the broken dry ice as latent heat of vaporization and does not convey heat to the storage chamber. The zone produced by the channels 20l thus reduces the difference in temperature between the' interior and exterior of the storage receptacle to a negligible diilerence with the result that onlyl a relatively small temperature Adiiierence need be maintained between 'the interior and exterior of the storage chamber to eifectively preserve the material. Heat absorption is thus coniined to the broken dry ice and the material in the chamber 24 may be stored for long periods of time without substantial loss thereof.

While the invention has been illustrated as` applied to a small portable unit capable ofr being easily transported the principle of the invention may be applied with equal successto large installations wherein thousands of pounds of thematerial 'are stored. The material may thus be preserved for periods of weeks or months nwithout substantial loss.- It should therefore be'understood that it is notintended that the invention be limited to. the particular construction herein shown and described except as defined by the claims.

What is. claimed is:

1. The method of storing dry ice which comprises the steps of enclosing a store of dry ice in a' permeable insulating jacket, placing the jacket 3. The method of storing. dry ice which com- "prises the steps of establishing a store of dry ice within an insulated casing, locating additional dry ice above said stored dry icevand within said casing, and circulating cold carbon dioxide gas produced byv evaporation of said additional dry ice downwardly about and beneath said stored dry' ice.

4; The method vof storing dry ice which'com-- prises the steps of establishing a store of dry ice within an insulated storage chamber, locating additional dry ice-above the stored dry ice and outside of said chamber, `and circulating cold carbon-dioxide gas resulting from evaporation of said additional dry ice in a circuit downwardly "about the storage chamber and thence upwardly r about said downwardly flowing gas into contact with said additional dry ice.

5. Apparatus forthe storage of dry ice comprising an 'insulated-.casing, a storage chamber for receiving dry ice "located'within said casing, a receptacle for receiving dry ice locatedl within saidcasingfand above said storage chamber, and means communicating with the lower portion of said receptacle for conducting carbon dioxidegas produced by evaporation of said additional dryv ice .downwardly about the sides and beneath the containing the store of dry ice in an insulated chamber contained within and spaced from a second vinsulated chamber, establishing a. heat absorbing zone in the space between said chambers, and maintaining said zone at a temperature approaching that of dry ice.

2. The method of storing dry ice whichcomprises the steps of enclosing a store of .dry ice in a permeable insulatingl jacket, placing the acket containing the dry ice in an insulated chamber positioned within and spaced from'a second insulated chamber, and creating arheatabsorbing zone in the space between said chambers by evaporation of additional dry ice.

bottom of said storage chamber and other means communicating with the upper .portion of said l sa.d receptacle about the sides of the storage chamber and beneath the same and having other portions extending upwardly to an upper opentoA ing in said receptacle externally, of the downwardly extending portions thereof, anda heat insulating casing enclosing said storage chamber, receptacle and conduits'.4

ALVIN c. vnntDsALL, Administrator of. the Estate Birdsall, Deceased.

of Wilfred T. 

